WASHINGTON -- Marking five disastrous weeks, BP readied yet another attempt to slow the oil gushing into the Gulf on Tuesday as a federal report alleged drilling regulators have been so close to oil and gas companies they've been accepting gifts and even negotiating to go work for them.

President Barack Obama prepared to head to the Gulf on Friday to review efforts to halt the millions of gallons of contaminating crude, while scientists said underwater video of the leak showed the plume growing significantly darker, suggesting heavier, more- polluting oil is spewing out.

BP's next effort to stop the damaged oil well, perhaps today, will be to force-feed heavy drilling mud and cement into the well to plug it up. The tactic, called a "top kill," has never been tried a mile beneath the sea, and company executives estimate its chances of success at 60 to 70 percent.

Also on Tuesday, in Jackson, Miss., 11 men who died in the April 20 rig explosion were honored at a somber memorial service with tributes from country music stars and drilling company executives.

"This is one of the most difficult days for many of us here. But for the families of our 11 lost colleagues, this is just another of many difficult days," said Steven Newman, CEO of Transocean Ltd., the Swiss-based owner of the Deepwater Horizon rig.

In Washington, Interior Secretary Ken Salazar said he has been laboring to root out problems at the agency that regulates offshore drilling. And the Justice Department said it will take all appropriate steps to ensure that those responsible for the disastrous blowout and oil spill are held accountable. On Capitol Hill, lawmakers continued feuding over a law that caps oil spill liability at $75 million for economic damages beyond direct cleanup costs. Democrats have tried to pass a bill raising the limit to $10 billion but have been blocked by Republicans.

A new report from the Interior Department's acting inspector general found that an inspector for the Minerals Management Service, which oversees drilling, admitted using crystal methamphetamine and said he might have been under the influence of the drug at work.

The report cited a variety of violations of federal regulations and ethics rules at the agency's Louisiana office. Previous inspector general investigations have focused on inappropriate behavior by the royalty-collection staff in the agency's Denver office.

The report adds to the climate of frustration and criticism facing the Obama administration, although it covers actions before the spill. Millions of gallons of oil are gushing into the Gulf, endangering wildlife and the livelihoods of fishermen, as scrutiny intensifies on a lax regulatory climate.

In a letter to Sen. Barbara Boxer, D-Calif., Assistant Attorney General Ronald Weich said he could not confirm or deny a criminal investigation was under way, but he said a team of investigators has been in the Gulf for three weeks. Justice lawyers have been meeting state officials and federal prosecutors to assure a coordinated effort, Weich said.

The Interior Department's acting inspector general, Mary Kendall, said her report began as a routine investigation "Unfortunately, given the events of April 20 of this year, this report had become anything but routine, and I feel compelled to release it now," she said.

Her biggest concern is the ease with which minerals agency employees move between industry and government, Kendall said. While no specifics were included in the report, "we discovered that the individuals involved in the fraternizing and gift exchange -- both government and industry -- have often known one another since childhood," Kendall said.

Relationships took precedence over their jobs, Kendall said. Salazar called the latest report "deeply disturbing" and said it highlights the need for changes he has proposed, including a plan to abolish the minerals agency and replace it with three new entities.